The present invention relates to an air brake adjustment system for use with an air brake chamber, where the system includes a seal, and a pivotally adjusted reference marker to provide a convenient visual indication of adjustment of the system.
Most air brake systems utilize a sealed housing, within which is a diaphragm attached to a push rod that extends through one side of the housing. The opposite side of the diaphragm creates an air cavity within the housing. The air pressure in the cavity rises when the brake pedal of the truck is depressed. The diaphragm deforms, and the air pressure rises, in proportion to the amount of force applied to the brake pedal. The push rod responds by moving with the diaphragm to engage the braking surfaces. When the air brake system is properly adjusted, the push rod will travel a distance on the order of up to about two inches from the point where the brake is completely released to the point where it is filly actuated. Over time, as the brakes are repeatedly applied, the push rod travel distance increases, eventually requiring a readjustment of the brake system before the braking capability deteriorates to a level that renders the truck unsafe.
Though the brake housing is generally sealed, problems can arise around the space between the housing opening and the extending push rod. Specifically, in prior art systems, the space is exposed to road moisture and debris allowing same to enter the brake housing which could lead to a premature failure of the brake system. As a consequence, more frequent safety and maintenance checks are required.
While the prior art offers some assistance in providing a stroke adjustment mechanism, they fall short in offering the advantages of the system of this invention. Such prior art is reflected in the following:
a.) U.S. Pat. No. 5,699,880, to Hockley, discloses a brake adjustment indicator for a braking system including a pressure chamber, a push rod extending longitudinally outwards from the pressure chamber and moveable when correctly adjusted between first and second positions, a brake arm and a pivot for pivotally mounting the push rod to the brake arm. The brake adjustment indicator comprises an indicator adapted to be mounted for longitudinal movement with the push rod, a support having a first portion and a second portion, the first portion adapted to be mounted to the vehicle, the support configured to position the second portion opposite to the indicator and first and second reference pointers fixedly positionable on the second portion for marking the first and second positions. A spacer is provided for positioning the first reference pointer in a preselected position relative to the second reference pointer. The first and second reference pointers are mounted for simultaneous movement on the second portion. PA1 b.) U.S. Pat. No. 5,269,253, to Spurlock, teaches a generally C-configured, push rod marker that may be secured to a push rod of an air brake piston without the need for special tools. PA1 c.) U.S. Pat. No. 5,244,061, to Hoyt et al., relates to an air brake stroke length gage in cooperative arrangement with an air brake system. The gage consists of a stroke length indicator and a reference marker. The stroke length indicator is mounted upon and moves with the push rod of the brake system. The reference marker is fixably attached to the air brake system adjacent to the push rod at a distance which corresponds to the appropriate stroke length for the brake system when properly adjusted. When the brake is fully activated, the spacial relationship between the stroke length indicator and the reference marker provides a visual indication of the brake system's adjustment. PA1 d.) U.S. Pat. No. 4,991,310, to Melia, discloses a brake stroke indicator for use on an air brake having an elongated brake push rod that travels a linear distance when the brake is applied. The length of the linear distance traveled depends upon the condition of the brake. The indicator comprises an elongated gauging probe having a plurality of grooves spaced at intervals along the length of the probe. Each such groove extends in a plane transverse to the longitudinal axis of the probe. A push rod bracket is also provided having a flange for engaging the probe in the grooves as the probe is slid longitudinally across the flange. The push rod bracket has clamping arms to allow attachment of the bracket at a preselected position along the length of the push rod such that the flange extends in a plane transverse to the longitudinal axis of the push rod. PA1 e.) U.S. Pat. No. 4,989,537, to Hutchinson, Sr. et al., relates to a brake wear indicator for an air brake system that includes an actuator having a diaphragm adapted to move within the actuator in response to air pressure, and a push rod mechanically coupled to the diaphragm and extending from the actuator through an opening in the actuator wall. The brake wear indicator comprises making means having a generally cylindrical outer surface, a longitudinal axis, a distance indicator on the outer surface, and means for securing the marking means to the push rod within the opening. The marking means thereby provides a visual indication of the position of the push rod along such axis at the opening.
By far, the most important safety feature of any vehicle is its ability to stop effectively. Therefore, in most truck fleet applications, the largest percentage of labor time and expense is brake maintenance. Numerous articles have been written emphasizing the need for proper brakes spec'ing, brake balance, and brake maintenance. Federal mandates are in effect for highway safety, driving the trucking industry toward safer braking systems. Anyone involved in truck maintenance is acutely aware of the liabilities associated with brake safety and maintenance. However, despite the strides the trucking industry has made toward safer braking, roadside inspections still reveal alarming statistics regarding brakes out of adjustment.
Although trucks receive P.M. Inspections at regular intervals, the daily safety inspections rest on the driver's ability to visually inspect and recognize defects. Nearly every item on the driver's vehicle condition report can be visually inspected, except the most critical, leaving the driver solely dependent on "feel". And, as brake related accidents and roadside inspections amply testify, "feel" is not a reliable guide. For example, an unloaded braking system for a truck may "feel" safe, but may not perform safely when loaded or descending a steep grade. The options available to the driver are to continue driving the truck in an unsafe condition, or call for road service and incur downtime. For these reasons, many drivers request daily brake adjustments, whether needed or not. Since there are no adequate visual means to determine brake adjustment, the mechanics must respond to these requests by checking and adjusting the brake stroke at each wheel position, and this can add significantly to transportation costs and downtime.
The present invention offers distinct advantages over the prior art in not only providing a visual indication of the push rod length, and hence the integrity of the brake system, but a seal to prevent dirt, moisture and debris from intruding into the brake chamber during periods of brake inactivity, i.e. highway driving. Additionally, by the use of a pivotally adjustable reference marker, the driver or maintenance personnel can adjust the marker to a more visible position than is available in the prior art systems. The manner by which the many advantages of the system hereof will become apparent to those skilled in the art from the following specification, particulary when read in conjunction with the accompanying drawings.